ClassificationChapter 18

• The domain system

– Prokaryotic domains Bacteria and Archaea

– Eukaryotes

• Are in the domain Eukarya

Bacteria Archaea Eukarya

Earliest

organisms

Prokaryotes

Eukoryotes

Figure 15.10B

Two patterns of evolutionary change

(b) Cladogenesis(a) Anagenesis

Hierarchical classificationPanthera

pardus

Panthera

Felidae

Carnivora

Mammalia

Chordata

Animalia

EukaryaDomain

Kingdom

Phylum

Class

Order

Family

Genus

Species

The connection between classification and phylogeny

Panthera pardus

(leopard)

Mephitis mephitis

(striped skunk)

Lutra lutra (European

otter)

Canis familiaris

(domestic dog)

Canislupus (wolf)

Panthera Mephitis Lutra Canis

Felidae Mustelidae Canidae

Carnivora

Ord

er

Fa

mil

yG

en

us

Sp

ec

ies

Monophyletic, paraphyletic, and polyphyletic groupings

(b) Paraphyletic. Grouping 2 does not

meet the cladistic criterion: It is

paraphyletic, which means that it

consists of an ancestor (A in this case)

and some, but not all, of that ancestor’s

descendants. (Grouping 2 includes the

descendants I, J, and K, but excludes

B–H, which also descended from A.)

(c) Polyphyletic. Grouping 3 also fails the

cladistic test. It is polyphyletic, which

means that it lacks the common ancestor

of (A) the species in the group. Further-

more, a valid taxon that includes the

extant species G, H, J, and K would

necessarily also contain D and E, which

are also descended from A.

D E

C

G H

F

J K

I

D E

C

G H

F

J K

I

D E

C

G H

F

J K

I

B

A

B

A

B

A

Grouping 2 Grouping 3Grouping 1

(a) Monophyletic. In this tree, grouping 1,

consisting of the seven species B– H, is a

monophyletic group, or clade. A mono-

phyletic group is made up of an

ancestral species (species B in this case)

and all of its descendant species. Only

monophyletic groups qualify as

legitimate taxa derived from cladistics.

Constructing a cladogram

Sala

mander

TAXA

Turt

le

Leopard

Tuna

Lam

pre

y

Lancele

t(o

utg

roup)

0 0 0 0 0 1

0 0 0 0 1 1

0 0 0 1 1 1

0 0 1 1 1 1

0 1 1 1 1 1

Hair

Amniotic (shelled) egg

Four walking legs

Hinged jaws

Vertebral column (backbone)

Leopard

Hair

Amniotic egg

Four walking legs

Hinged jaws

Vertebral column

Turtle

Salamander

Tuna

Lamprey

Lancelet (outgroup)

(a) Character table. A 0 indicates that a character is absent; a 1

indicates that a character is present.

(b) Cladogram. Analyzing the distribution of these

derived characters can provide insight into vertebrate

phylogeny.

CH

AR

AC

TE

RS

Trees with different likelihoodsHuman

Tree 1: More likely

Mushroom Tulip

40%

40%

0

30%

0

0Human

Mushroom

Tulip

(a) Percentage differences between sequences

(b) Comparison of possible trees

Tree 2: Less likely

15%

5%

15% 20%

5%10%

15%

25%

Monera Protista Plantae Fungi Animalia

Earliest

organisms

Prokaryotes

Eukoryotes

Figure 15.10A

• Arranging life into kingdoms is a work in progress

– In the five-kingdom system

• Prokaryotes are in the kingdom Monera

• Eukaryotes (plants, animals, protists, and fungi) are grouped in separate kingdoms

Prokaryotes (Monera)Bacteria live EVERYWHERE!

• Bacteria live in all ecosystems

– on plants & animals

– in plants & animals

– in the soil

– In EXTREMES (hot, cold, acid, salt, deep)

– on the living

– on the dead

Microbes alwaysfind a way tomake a living!

Prokaryote Structure

• Unicellular

– bacilli, cocci, spirilli

• Size

– ~1/10 size of smallest eukaryotic cell

• 1 micron (1um)

• Internal structure

– no internal compartments

• no membrane-bound organelles

• only ribosomes

– circular chromosome, naked DNA

• not wrapped around proteins

prokaryotecell

eukaryote cell

Protista:General characteristics

• Classification criteria

– eukaryotes

– not animal, plant or fungi

That’s more ofwhat they’re not& notwhat they are!

Protist Diversity

• The full spectrum of modes of life

– unicellular to multicellular

– autotrophic to heterotrophic

– asexual to sexual reproduction

– pathogenic to beneficial

– sessile to mobile

Problems with Protist Classification

Something’snot right here!

• Too Diverse!– doesn’t reflect any evolutionary relationship amongst

all kingdom members

– paraphyletic

Plantae:

Bryophytes

non-vascular

land plants

Pteridophytes

seedless

vascular plants

Gymnosperm

pollen &

“naked” seeds

Angiosperm

flowers & fruit

pollen & seeds

vascular system = water conduction

mosses ferns

conifersflowering plants

colonization of land

Tracheophytes

xylem cells = tracheidsAncestral Protist

flowers

Fungi:General characteristics

• Classification criteria

– eukaryotes

– heterotrophs

• Absorb nutrients

– mostly multicellular

• EXCEPT unicellular yeasts

– cell wall

• chitin

– rigid polysaccharide

– sexual & asexual reproduction

Fungal Structure

• Fungal body

– mycelium

• thread-like cells

• hyphae

• Cells

– multiple nuclei

• Cell wall

– chitin

• just like crab shells

Ecological Roles

• Decomposers– recycle nutrients

• Symbiotic Relationships– lichen

• fungi + algae– cyanobacteria or green algae

• pioneer species in ecosystems

• makes soil from bare rock

– mycorrhizae• fungi + plants

• enables plants to absorb more water

Lichens are fungi that have discovered agriculture!

Fungal Diversity

Fungi

Animal Characteristics

• Heterotrophs

– must ingest orgnaisms (“food”) for nutrients

• Multicellular

– complex

• No cell walls

– Allows quickmovement

• Sexual reproduction

– no alternation of generations

– no haploid gametophyte

Porifera

Cnidaria

Platyhelminthes

sponges jellyfish flatworms roundworms

Nematoda

Mollusca Arthropoda Chordata

Annelida Echinodermata

mollusks

multicellularity

Ancestral Protist

tissues

bilateral symmetry

body cavity

segmentation

Animal Evolution

coelom

starfish vertebrates

endoskeleton

segmentedworms

insectsspiders

backbone

specialization & body complexity

specialized structure & function,

muscle & nerve tissue

distinct body plan; cephalization

body complexity

digestive & repro sys

digestive sys

body size

redundancy,

specialization, mobility

body & brain

size, mobility

radial

bilateral

Review Questions

1. The temperature at which hybrid DNA melts is indicative of the degree of homology between the DNA sequences. The more extensive the pairing, the higher the temperature required to separate the strands. You are trying to determine the phylogenetic relationships among species A, B, and C. You mix single-stranded DNA from all three species (in test groups of two) and measure the temperatures at which the hybrid DNA melts (separates). You find that hybrid BC has the highest melting temperature, AC the next highest, and AB the lowest.

(cont.) From these data you conclude that *A. species A and B are most closely related, whereas B and

C are least closely related.

B. B and C must be the same species, and A is more closely related to C than to B.

C. species B and C must have diverged most recently, and A is more closely related to C than to B.

D. A hybridizes most easily with B, and they must have a more recent common ancestor than do A and C.

E. these tests are inconclusive and you had better go back and check the fossil record.

2. According to this dichotomous phylogenetic tree created using cladistic analysis, C and D are most closely related because they

A. do not share a common ancestor with O, A, or B.

B. are monophyletic.C. evolved from a common

ancestor a long time ago.D. have the most shared

derived characters in common.

E. have the greatest number of anatomical similarities as shown by statistical analysis.

3. A biologist discovers two new species of organisms, one in Africa and one in South America. The organisms resemble one another closely. Which type of evidence would probably be least useful in determining whether these organisms are closely related or are the products of convergent evolution?

A. the history and timing of continental drift

B. a comparison of DNA from the two species

C. the fossil record of the two species

D. analysis of the behavior of the two species

E. comparative embryology

Use Figure 25.1 to answer the following questions.

4. A common ancestor for species C and E could be at position numberA. 1.

B. 2.

C. 3.

D. 4.

E. 5.

E. The two extant species that are most closely related to each other are

1. A and B.

2. B and D.

3. C and B.

4. D and E.

5. E and A.

5. If this evolutionary tree is an accurate depiction of relatedness, then which of the following should be correct?

A. The entire tree depicts anagenesis.

B. If all species depicted here make up a taxon, this taxon is monophyletic.

C. The last common ancestor of species B and C occurred more recently than the last common ancestor of species D and E.

D. Species A is the ancestor of both species B and C.

E. The species present at position number three is ancestral to three extant species.

1. B only

2. A and C

3. C and D

4. B, C, and D

5. B, C, and E

A researcher compared the nucleotide sequences of a homologous gene from five different species of mammals. The sequence homology between each species' version of the gene and the human gene are presented as a percentage of similarity.

Species Percentage

Chimpanzee 99.7

Orangutan 98.6

Baboon 97.2

Rhesus Monkey 96.9

Rabbit 93.7

6. What conclusion can be validly drawn from these data?

A. Humans and other primates evolved from rabbits.

B. All organisms have similar DNA.

C. Among the organisms listed, humans shared a common ancestor most recently with chimpanzees.

D. Humans evolved from chimpanzees.

E. Both A and D are correct.

7. Which statement represents the best explanation for the observation that the nuclear DNA of wolves and domestic dogs has a very high degree of homology?

A. Dogs and wolves have very similar morphologies.

B. Dogs and wolves belong to the same genus.

C. Dogs and wolves are both members of the family Canidae.

D. Dogs and wolves shared a common ancestor relatively recently.

E. Convergent evolution has occurred.